When a tree grows it absorbs carbon.
A moment’s thought and this is obvious. Saplings are small with few leaves and only a little wood. A mature tree has a thick trunk made up of 50% carbon along with a canopy of branches, twigs and leaves. Belowground the roots make up at least a third of the tree’s total biomass.
Mature trees don’t absorb much carbon at all. Indeed some old-growth forests are net emitters of carbon. As dead leaves and branches decay, they emit more greenhouse gas than is absorbed by the modest amount of the new growth in the trees.
Carbon is captured and stored in the tree until the tree matures.
Sweden has a lot of forests; around 30 million ha or 70% of the land area with some 22.5 million hectares of this as productive forest land.
The area of forests has doubled in the last 100 years because Sweden grows more trees than it chops down. All this sequestration makes Sweden carbon neutral.
Timber volume grows at around 120 million forest cubic metres per year with a sustainable forestry model that harvests around 90 million forest cubic metres. Although, there are other ways to report this dynamic that are less flattering.
Sweden has increased the volume of timber steadily since the 1950’s. The key number here is the growth in timber volume and where it comes from.
There is a dilemma though.
Validity for this green claim of carbon neutrality comes about only when the bulk of the trees in the forest estate are young.
In other words, they have to be harvested after 50 years of growth and new trees planted to keep the sequestration rate high. Despite making up less than one per cent of the planet’s forested land, Sweden is the world’s second-biggest exporter of pulp, paper and sawn wood products.
Whilst felling trees is good for business — imagine Ikea without access to timber products — there are costs to the biodiversity of even-aged stands regularly harvested.
Conservationists will rightly tell you that many animals, plants and microbes only persist in old-growth forests and these species are under pressure when their habitat declines. Replacing old-growth forests with monoculture plantations is bad for biodiversity.
The sustainability issue here is not just about carbon.
If the growth in timber volume comes from managed or previously cleared land going into timber production all is well.
If the growth comes from the clear-felling of old forests, this is not a sustainable solution.
What sustainably FED suggests
The only way to validate claims for sustainability or if Swedish forestry makes the country carbon neutral is to know the ecology and this means understanding the processes in nature.
We say this glibly but realise the magnitude of this question.
Ecology is complex.
It captures time from evolutionary to ecological to regular day to day time and an appreciation of space from landscape to location. It needs some chemistry, physics and the niche sciences of geology, soil, geomorphology, meteorology and climate. It also helps to know some math, statistics and especially the scientific method.
Ecologists are the true jack of all scientific trades and masters of integration.
Study some ecology and you will be astonished by how ecological knowledge can help find truly sustainable solutions to the human predicament.